Leases (assets and liabilities) (Details)	3 Months Ended		6 Months Ended
	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)
Leases
Number of option period for time charter | item	0		0
Operating lease liabilities - Time Charter in VLGCs	$ 21,500,000		$ 21,500,000
Weighted average discount rate (as a percent)	3.88%		3.88%
Weighted average remaining lease term	27 months 27 days		27 months 27 days
Operating lease right-of-use assets - Office Leases	$ 834,413		$ 834,413
Operating lease right-of-use assets - Time Charter in VLGCs	21,495,684		21,495,684
Operating lease liabilities current - Office Leases	425,345		425,345
Operating lease liabilities current - Time Charter in VLGCs	8,982,704		8,982,704
Operating lease liabilities non-current - Office Leases	411,929		411,929
Operating lease liabilities non-current - Time Charter in VLGCs	12,512,980		12,512,980
Charter hire expense
Leases
Operating lease income	$ 4,600,000	$ 5,400,000	$ 11,500,000	$ 6,700,000
Minimum
Leases
Weighted average discount rate (as a percent)	3.82%		3.82%
Maximum
Leases
Weighted average discount rate (as a percent)	5.53%		5.53%